Variable displacement pump



y 1963 T. BUDZICH 3,090,313

VARIABLE DISPLACEMENT PUMP Filed April 25, 1961 4 Sheets-Sheet 1 INV ENTOR.

May 21, 1963 T. BUDZICH VARIABLE DISPLACEMENT PUMP Fild April 25, 1961 4Sheets-Sheet 2 INVENTOR;

TADEUSZ 56/02/67,

May 21, 1963 T. BUDZICH 3,090,313

VARIABLE DISPLACEMENT PUMP Filed April '25, 1961 4 Sheets-Sheet 3ATTO/QA/EYS May 21, 1963 T. BUDZICH VARIABLE DISPLACEMENT. PUMP 4Sheets-Sheet 4 Filed April 25, 1961 INVENTOR.

United States Patent 3,539,313 VARIABLE DlSiLACEh/IENT PUMP TadeuszBndzich, Shaker Heights, Ghio, assignor to The Weatherhead Company,Cleveland, Ohio, a corporation of Ohio Filed Apr. 25, 196i, Ser. No.105,357 9 Claims. (Cl. 103-37) This invention relates generally topositive displacement hydraulic pumps, and more particularly to thereciprocating piston type of positive displacement pumps in whichpistons are reciprocated through a fixed stroke, but the effectivedisplacement of the pump can be varied to change the volume of the fluidoutput.

A principal feature of this invention is the provision of a positivedisplacement axial piston pump of the fixed stroke type in which thecylinder block is slidabie within the pump housing and carries portswhich permit fluid within the pump housing to enter the cylinder bores,in which the effective volume of the pump is varied by axially shiftingthe position of the cylinder block and hence the ports relative to thepiston stroke. For maximum output volume of the pump, the cylinder blockis positioned so that the port is fully opened at the rearward reversalof the piston to allow the cylinder bore to fill with fluid, after whichforward motion of the piston seals off the port after only a shortdistance of movement. and forces the remainder of the fluid Within thecylinder bore out through check valves into the outlet port. By shiftingthe cylinder block in the one direction toward the forward end of thepiston stroke, the port is not closed by the piston until a laterportion of the stroke, so that some of the fluid in the cylinder isforced back out through the port and therefore a lesser volume is pumpedoutward through the check valves. Pumps of this type have been disclosedin co-pending applications by the present inventor Serial No. 825,005,filed July 6, 1959 and Serial No. 847,512, filed October 20, 1959.

According to the present invention, the cylinder block may also be movedfurther toward the rearward end of the piston stroke so that the port isnot completely opened during the reversal of the piston and the fluidWithin the pump housing is throttled by the decreased size or" the portopenings so that the cylinder bore is not completely filled and onlythat volume of fluid which enters the cylinder =bore is pumped outthrough the check valves. A pump incorporating this type of control isdisclosed in my co-pending application Serial No. 82,292, filed Janumy12, 1961. In the present invention, both of these types of control areincorporated into the same pump to provide two alternative methods ofcontrol for reducing the efi'eotive output volume of the pump.

Another feature of this invention resulting from the incorporation in asingle pump of both methods of control is that the position of thecylinder block can be controlled m-anually in such a manner that byemploying the spill type control, the cylinder block may be preciselypositioned over a relatively long range of movement to provide veryprecise and accurate control of the output volume, and the pump blockcan also be positioned by the throttling type control to obtain a veryrapid response because of the short distance through which the cylinderblock moves to reduce the output volume with this control.

Another feature of this invention resulting from the dual methods ofcontrol of the effective output volume of the pump is that an automaticcontrol is supplied to position the cylinder block using the spill typeof control while a manual control means is provided to shift thecylinder block in the other direction to control the effective outputvolume by the throttling of the fluid entering the cylinder bores.

Another feature of this invention is that a manual control for shiftingthe cylinder block may be supplied for shifting the cylinder block inwhich the change in output volume is directly proportional to the amountof movement of the cylinder block and hence of an external lever whichis provided for shifting the position of the cylinder block.

Another feature of this invention is that no fluid pres sure or springforces are applied to the cylinder block when the dual manual control isemployed so that the cylinder block remains easily shiftable by handthroughout both ranges of control and may be selectively clamped inposition any place Within the ranges without producing noticeable stresson any of the pump parts.

Another feature of this invention is that an automatic control for thecylinder block is supplied in combination with a manual control in whichthe automatic control during manual operation will operate as an excesspressure valve and shift the cylinder block to reduce the effectiveoutput volume in case the outlet pressure should exceed a predeterminedvalue even though the pump is heing regulated by manual control.

Another feature of this invention is that in the aforedescribedarrangement employing a combination automatic and manual control, noforce is normally applied to the cylinder block in manual operation andthe automatic control is rendered inoperative and applies no forces toshift the cylinder block unless the outlet pressure should exceed thepredetermined limit.

Many additional features and advantages of this invention relating tothe simplicity of construction, ease of operation and low cost ofmanufacture will readily become apparent to those skilled in the artupon a reading of the following detailed description of severalembodiments of the invention as illustrated in the drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a pump according to thepresent invention in which the cylinder block is shifted manually tocontrol the effective output volume by both spill type control andthrottling control;

FIG. 2 is a fragmentary cross-sectional view of the cylinder block andpiston when the cylinder block has been shifted to minimum output volumeemploying the throttling type control;

FIG. 3 is a fragmentary cross-sectional view similar to that of FIG. 2but showing the cylinder block shifted to the minimum effective volumeposition according to the spill type control;

PEG. 4 is an end elevational view of the pump of FIGS. 13 showing theexternal control lever;

FIG. 5 is a side elevational view of the pump showing the externalcontrol lever;

FIG. 6 is a longitudinal cross-sectional view of another embodiment ofthe invention employing an internal automatic control for reducing theeffective volume by the spill type control and employing a manualcontrol to reduce the effective volume by throttling type control;

FIG. 7 is a fragmentary cross-sectional view of the pump of FIG. 6showing the cylinder block shifted to the minimum output volumeaccording to the manual control;

FIG. 8 is a fragmentary cross-sectional view similar to that of FIG. 7but showing the cylinder block shifted to the minimum output volume bythe automatic control; and

FIG. 9 is a side elevational view of the pump of FIGS. 6-8 showing thearrangement of the external control lever.

Referring now to the drawings in greater detail, there is illustrated inFIG. 1 a pump having a pump housing 10 which encloses a fluid chamber 11Within which the pump mechanism is located. The pump housing 10 isgenerally cylindrical in shape and at one end is formed with an internalcylindrical end portion 12 which is closed off by an outlet housing 13.The outlet housing 13 abuts against an inwardly projecting flange 14 onthe pump housing and is secured in place by means of suitable set screwsindicated at 15. An O-ring seal 16 is provided on the outer periphery ofthe outlet housing 13 to prevent leakage at the joint between the outlethousing and the pump housing. A threaded inlet opening '18 is formed onthe side of pump housing 10 adjacent its mid-point for connection to afluid reservoir for admission of fluid from the reservoir into thechamber 11.

At its other end, the pump housing 10 is closed ofl by a drive housing20 secured in place by means of cap screws 21. As shown, drive housing20 is provided with a radial flange 22 for mounting the pump in positionon machinery or a prime mover. An axial bore 24 extends through thedrive housing 20 to receive a bearing member 25 at its inner end. Thebearing member 25 has an axial portion 26 extending along the bore 24and a radial portion 27 extending outwardly along the inner wall of thedrive housing 20. A drive member 30 is rotatably journaled within theaxial portion 26 of bearing member 25 and has a shank portion 31extending axially outward through the drive housing to make sealingContact with oil seal '32 fltted within the outer end of axial bore 24.The drive member 30 has a radially extending flange portion 33 makingbearing contact with the radial portion 27 of the bearing member whichprovides a thrust bearing to absorb the axial forces of the pumpingaction. A drive shaft 35 extends axially through a bore within the drivemember 30 and is secured thereto by a spline connection 36. The driveshaft 35 projects axially outward beyond the end of the shank portion 31for connection to a suitable motor or other prime motor for driving thepump.

Mid-way between the outlet housing 13' and drive housing 20, a webmember or plate 38 extends transversely across the fluid chamber 11 andis provided with an axially extending peripheral flange '39 which fitsagainst the walls of the pump housing 10-. The web memberSS is heldagainst axial movement by an inwardly extending annular shoulder 40formed on the pump housing 10, and at the other end by a snap ring 41.The web member 38 has an axially extending portion 43 which projectstoward the drive housing 20. The axial extension 43 is provided with anaxial bore 44 which communicates with transverse opening 45 to allowfree circulation of fluid within the chamber 11 from one side of the webmember 38 to the other. The outer end of axial extension 43 carries abearing insert 46 which receives the pilot end portion 47 of the driveshaft 3'5.

The drive member 38' is provided with an inclined face 50 and a hubportion 51 which extends perpendicular to the inclined face 50. Abearing member 52 is mounted on drive member 30 and includes a radiallyextending flange portion 53 lying along the inclined face 50, and anaxial sleeve portion 54 extending along the hub portion 51. Bearingmember '52 serves to journal a wobble plate 55 which is supported on theradial and axial hearing portions 53 and 54, respectively. At its lowerend, the wobble plate 55 is provided with a projecting stud 57 on whichis rotatably secured a guide block 58. Guide block '58 is adapted toslide longitudinally within a channel 59 formed in the pump housing 10to prevent rotation of the wobble plate 55 as it is oscillated by therotation of the guide members 30. V

A cylinder block 62 is slidably journaled in the cylindrical end portion12 of pump housing 10 for axial sliding movement therein. The cylinderblock 62 is restrained from rotating Within the pump housing by a setscrew 63 mounted in the wall of .the pump housing 10 and having a dogpoint engaging a longitudinal groove or guide slot 64 on the outerperiphery of the cylinder block. The cylinder block 62 is provided witha plurality of axially extending cylinder bores 65 which are spacedequidis- 4 tantly about the cylinder block at points equidistant fromthe axis of the drive shaft 35. Only one cylinder bore has been shownfor purposes of clarity, but it is understood that the pump has aplurality of cylinders similar to the one shown in the drawings anddescribed hereinafter. The cylinder block 62 is also provided with oneor more passages 67 extending therethrough from one side to the otheraround the outer periphery and with a centrally disposed axial bore 68so that fluid can circulate freely within the chamber 11 on both sidesof the cylinder block.

A piston or plunger 70 is fitted within the one end of the cylinderbores and has a head portion 71 on the end away from the wobble plate55. Piston has a tubular skirt portion 72 extending rearwardly away fromthe head portion 71. A compression spring 74 is fitted around thetubular skirt portion 72 and abuts at the one end against the web member38. At the other end, compression spring 74 abuts against a springretainer 75 secured at the outer end of the tubular skirt portion 72.Thus the compression spring 74 serves to bias the piston 70 toward arearward position within the cylinder bore and toward the wobble plate55. The piston 70 is drivingly connected to the wobble plate 55 by meansof a pis ton rod 77 which is positioned within the tubular skirt portion72. At its one end, piston rod 77 has a ball end 78 which seats in asuitable recess directly beneath the head portion 71 on the piston 70,and at its other end the piston rod has another ball end 79 which isseated within a cup-like recess 81 on the face of the wobble plate 55.At its midpoint the piston rod 77 is provided with a radially extendingflange or centering disc 82 to maintain the piston rod in axialalignment within the tubular skirt portion 72 if either end of thepiston rod should become unseated from its seat against either thepiston head 71 or the wobble plate 55.

The cylinder block 62 has an annular groove or outer filling slot 85extending circumferentially about its periphery and opening into each ofthe cylinder bores 65 to admit fluid therein. A second annular groove orinner filling slot 87 extends radially outward from the axial bore 68within the cylinder block 62 to open into the cylinder bores 65 at theirinner sides. Forward edge 86 of the outer filling slot 85 and theforward edge 88 of the inner filling slot 87 both lie in the same plane,and the spacing of the forward edges 86 and 88 from the piston head 71determines the eflective port area of the two filling slots 85 and 87.

A reaction piston 96 i slidably journalled within the ends of thecylinder bores 65 opposite the pistons 70 to make a sealing fit withinthe cylinder bore to prevent leakage of fluid between the reactionpiston and the cylinder bore walls. Each of the reaction pistons 96 hasan axial bore 91 extending therethrough, and at the end away from thepiston 70, the reaction piston 96* has a snap ring 92 which forms oneabutment for a compression spring 93 fitted around the end of thereaction piston. The other end of compression spring 93 abut-s against aretainer plate 94 secured to the inner face of the outlet housing 13 bysuitable screws 96.

The outlet housing 13 is provided with a bore or chamber 98 oppositeeach of the reaction pistons to receive a port member 99. Port member 99is provided with an O-ring seal 101 to make sealing contact with thebore 98 and has a projecting end portion 102 to make sealing contactwith the end of the adjacent reaction piston 90. A bore 103 extendsthrough the port member 99 to connect with the axial bore 91 in thereaction piston 90. The opposite end of the bore 98 is closed ofi by asuitable plug 104-, and positioned within the bore is a cage 106 whichencloses a compression spring 107 biasing a check valve plate 168against the other end of the port member 99 to close off bore 103-. Thusthe check valve plate 108 serves to permit fluid within the reactionpiston 98 and port member 99 to pass outwardly past the plate, butprevents fluid from entering the port member 99 from the outlet side. Aconnecting passage 109 extends from each of the bores 98 radially inwardto connect with an wially located outlet passage bore 111 in the outlethousing 13. Outlet bore 111 is provided with a suitable threaded portion112 at its outer end to receive a suitable pipe fitting for connectionto the outlet line of the pump.

The manual control mechanism for shifting the cylinder block 62longitudinally within the pump housing 1G is shown most clearly in FIGS.4 and 5 together with FIG. 1. The pump housing includes a cross shafthousing portion 115 projecting from the lower side of the pump housingbeneath the cylinder block 62. A cross shaft 117 is journaled in thecross shaft housing portion 115 and carries a lever arm 118 at its innerend. Lever arm 118 is secured to the inner end of the cross shaft 117 bya set screw 119 and at its upper end is provided with an end portion 121to fit within the outer filling slot 85 on the cylinder block 62. Itwill be understood that the end portion 121 fits into the outer fillingslot '85 between two of the cylinder bores so as not to block off orobstruct the port area provided by the filling slot at these cylinderbores. An indicia plate 123 is mounted on projection bosses 124 by meansof suitable cap screws 125 to extend along the side wall of the pumphousing 1%. A control handle 127 is secured at its lower end to theouter end of the cross shaft 117 and extends along the inner side ofindicia plate 123. A screw clamp 130 is fastened to the upper end ofcontrol handle 127 to slide within an arcuate slot 128 on indicia plate123. By tightening the screw clamp 130, the control handle 127 can belocked in place on the indicia plate 123. It will be noted that apointer 131 may be provided on the control handle 127 for alignment withindicia marks 132 along the arcuate upper edge of indicia plate 123 fornoting and recording the relative position of the control handle withrespect to the indicia plate.

The operation of the pump can be seen most clearly in conjunction withFIGS. 2 and 3. When the cylinder block is in the position of FIG. 1 andthe piston 7a is in the rearward or retracted position, the forwardedges 86 and 8 8 of the inner and outer filling slots 85 and 87,respectively, are spaced forward of the piston head 71. Under theseconditions, the fluid within the chamber 11 is free to flow inwardthrough the filling slots to completely fill the cylinder bore 65. Asthe piston 70 moves forward, the piston head 71 will be shifted towardthe reaction piston 90 to reduce the volume within the cylinder. Sincethe filling slots 85 and 87 are open during the initial portion of thestroke, fluid will be forced outward into the chamber 11 through theseslots. However, after the piston head 71 passes the forward edges 86 and88 of the filling slots, these filling slots are sealed ed and theremainder of the fluid within the cylinder bores will be positivelydisplaced outward through the reaction piston 9th and port member 99,and hence past the check valve plate 168, through connecting passage169', and into the outlet passage bore 111. When the piston 7 ti isretracted, the check valve plate 108 will close and a partial vacuumwill be formed within the cylinder bores until the piston head 71 hasretracted past the forward edges 86 and 88 of the filling slots so thatthey are open to allow fluid within the chamber 11 to flow through thefilling slots and refill the cylinder bores.

The effective output volume of the pump may be reduced by two differentmethods, depending upon which direction the cylinder block is. shiftedfrom the position of maximum output volume as shown in FIG. 1. When thecylinder block is shifted toward the rearward position as shown in FIG.2, the cylinder block as is brought into contact with the web member 38.The filling slots 85' and 87 are hence moved toward the rearwardposition of the piston, and in the position shown, the forward edges 86and 88 of the filling slot will be adjacent the head portion 71 of thepiston when the latter is in the retracted position. As a result, theports provided by the filling slots 85 and 87 will never be open and nofluid can enter the cylinder bores. Thus the partial vacuum which occurswhen the piston is retracted will remain within the cylinder bore and nofluid will be forced outward past the check valve plate 108 when thepiston is at the forward end of the stroke and thus the pump will haveno effective output volume.

It will be understood that in accordance with the teaching of theinventors co-pending application Serial No. 82,292, previously referredto, that when the cylinder block 62 is in a position intermediate thatof FIGS. 1 and 2, where the forward edges 86 and 38 of the filling slotsare positioned closer to the piston head 71 when the latter is in theretracted position, the effective port area presented by the fillingslots 85 and 87 will not be sufficiently great to allow the fluid withinthe pump housing chamber 11 to completely fill the cylinder bores. Thereduced effective port area thus serves to throttle the flow of fluidinto the cylinder bores to reduce that flow to an amount less than thatrequired to completely fill the partial vacuum created within thecylinder bores by the retraction of the piston. Only the volume of fluidwhich was permitted to enter by the position of the ports will be pumpedoutward through the check valve plate 193 and only this amount willconstitute the effective output volume of the pump. Since it isnecessary to move the cylinder block 62 through only a very shortdistance to change the effective output volume of the pump from maximumto zero by this method of control, a very fast response can be obtained.

When the cylinder block 62 is shifted in the opposite direction awayfrom the web member 33 and toward the outlet housing 13, it reaches alimiting position as shown in FIG. 3 in which the effective outputvolume of the pump is also reduced to zero. As previously stated, whenthe piston starts its forward stroke, the fluid within the cylinderibore will be spilled out through the filling slots S5 and 87 until thepiston head 71 has passed to the forward edges 86 and 83 of the fillingslots to seal off these slots and prevent passage of fluid from withinthe cylinder bore outward into the pump housing chamber 11. As thecylinder block 62 is shifted toward the outlet housing 13, the piston 70must move farther forward along its stroke before the filling slots 85and 87 are closed off. Thus, a lesser portion of the piston stroke isemployed for forcing fluid past the check valve plate 1% and smallervolume of fluid will therefore be discharged into the outlet passagebore 111 for each piston stroke. When the cylinder block 62 is shiftedto the limiting position of FIG. 3, the forward edges '86 and '88 of thefilling slots 85 and 87, respectively, are positioned on a line with theedge of the piston head 71 when the latter is at the forward end of itsstroke. Thus, the piston head 71 will never be able to close off thefilling slots 85 and 87 before the end of the stroke and all of thefluid within the cylinder bores will be discharged outward through thefilling slots and none will be pumped outward past the check valveplates 198.

This latter method of controlling the pump volume requires that thecylinder block 62 be shifted through a distance equal to a substantialportion of the stroke of the piston 70 to vary the effective outputvolume from maximum down to Zero. As a result, this method of controlallows the effective output volume to be very precisely controlled sincethe cylinder block 62 can be positioned with a high degree of accuracyover the relatively long length of the control stroke. On the otherhand, the response with this method will not be as fast as that obtainedwith the throttling method since it naturally will take more time toshift the cylinder block through the longer distance with this typecontrol. Thus the pump provides two methods of control, one employingthrottling control which requires that the cylinder block be moved onlya short distance to provide fast response, and the other employing spillcontrol in which a high degree of accuracy can be obtained because ofthe relatively long length of movement of control handle.

It should be noted that there is no substantial resistance to a movementof the cylinder block 62 between either of the limiting positions asshown in FIGS. 2 and 3. This is true because the design of the pumppro-v vides that none of the pumping forces or reactive forces aretransmitted to the cylinder block itself. Since the reaction piston isof the same diameter as the pumping piston 79, the pumping reactionforces will be absorbed entirely by these members and will lie directlyalong the axis of movement of the cylinder block. Thus the only forcesopposing the movement of the cylinder block between these positions isthe sliding friction of the moving parts and the necessity of displacingthe oil from one side to the other of the cylinder block as it isshifted within the chamber 11. 7 An alternative embodiment of theinvention is shown in FIGS. 6 through 9 in which the position of thecylinder block is controlled by a manual and an automatic control. Thepump shown in these figures includes a pump housing or body whichencloses a fluid charnher 141. Fluid from a reservoir or other sourcefills the chamber 141 through an inlet opening 14-2. At the one end,pump housing 140 is closed off by an end plate 143 which is fixedlysecured to an outlet housing 144 by suitable locating pins indicated at145. The end of plate 143 has a tubular guide portion 147 extendingaxially into the chamber 141, and guide portion 147 has an axial bore148 extending therein from the outer end. A stop plate 150 has a shankportion fitted within axial bore 148 and a radially extending webportion 151 extending toward the walls of the pump housing 140.

At the other end of pump housing 140, an annular bearing member 153 ismounted on the pump housing to journal a drive member 155. This drivemember has an axial ibore to receive a drive shaft 156 extendingtherethrough and making a spline connection indicated at 157 torotatably drive the drive member 155. The drive shaft 156 extends intothe chamber 14-1 and at its inner end carries a pilot portion 153 whichis journaled within a bore on the stop plate 150. The other end of driveshaft 156 extends outward through a bore 169 in the Walls of pumphousing 149 to make sealing contact with anoil seal 161 at the outer endof bore 160. The drive member carries an inclined annular bearing member164 to rotatably journal a wobble plate 165. In order to prevent thewobble plate 165 from rotating within the pump housing 141} as it isoscillated by rotation of drive member 155, it is provided with aprojecting stud 167 at its lower end to rotatably journal a bearingblock 168. The bearing block 168 is made a sliding fit within alongitudinal channel or guide 169 formed on the walls of pump housing140.

A cylinder block is slidably mounted on a tubular guide portion 147 forlongitudinal movement withm the purnp housing 140. The cylinder block175 carries a guide pin 176 to fit within a longitudinal slot 177 on thetubular guide portion 147 to prevent rotation of the cylinder blockwithin the pump housing. At its one end, cylinder block 175 is limitedin longitudinal movement by the web portion 151 of the stop plate 159.At the other end, the cylinder block 175 is adapted to move intoabutment with a spring abutment plate 178 slidably journaled within acylindrical portion 179 of the pump housing 140. A snap ring 181 ispositioned within the cylin drical portion 179 to limit movement of thespring abutment plate 178 toward the stop plate 15%. The cylinder block175 is provided with a plurality of longitudinal cylinder bores 189extending from end to end through the cylinder block and spacedequidistantly about the axis of the drive shaft 156. An annular fillingslot 183 extends circumferentially about the outer periphery of cylinderblock 175 and opens into the cylinder bores 186 to serve as aport foradmitting fluid therein. A piston is slidably mounted within thecylinder bore 188 and has a head portion 136 extending forward withinthe cylinder bore to a point adjacent the forward edge 134 of thefilling slot 183. The piston 185 also has a tubular skirt portion 187projecting rearwardly out of the cylinder bore and toward the wobbleplate 165. A compression spring 139 is fitted around the tubular skirtportion 187 and abuts at its one end against the web portion 151 of stopplate 156. -At its other end, spring 189 abuts against a spring retainer196 secured to the outer end of tubular skirt portion 187. A piston rod192 is fitted within the tubular skirt portion 187 and at its one endcarries a ball portion 193 which bears against the underside of thepiston head portion 186. The other end of piston rod 192 is formed withanother ball portion 194- and fits within a cup-like recess 196 on theface of wobble plate 165. The midportion of piston rod 192 is enlargedas at 197 to maintain the axial alignment of the piston rod 192 in caseeither of the ends of the piston rod should be removed from theirrespective sockets.

A reaction piston 200 is fitted within the other end of the cylinderbore 181) and extends toward the end plate 143. The reaction piston 290has an axial bore 201 therein to conduct fluid from the cylinder bore tothe pump outlet. At the end adjacent the end plate 143, reaction piston200 is provided with a snap ring 282 which serves as an abutment for ahelical compression spring 203 which fits over the outer surface of thereaction piston and abuts at its other end against the spring abutmentplate 178. The outlet housing 144 has a recess 205 in axial alignmentwith the cylinder bore to receive a port member 266. The port member 206is provided with an O-ring seal 207 on its outer periphery to makesealing contact with the recess 205 and has a projecting end 298 whichextends out through an opening 259 in end plate 143 to make sealingcontact with the end of the reaction piston 20%. An axial bore 210extends through a port member 206 in alignment with the axial bore 201in the reaction piston. A cage 212 is fitted within recess 205 tosupport a compression spring 213 which biases a check valve plate 214against the end of port member 206 to prevent a reverse flow of fluidfrom the recess 295 back into the reaction piston and cylinder bore. Aconnecting passage 216 extends radially inward to connect to an axiallyaligned outlet passage 218 formed in the outlet housing 144. The outerend of outlet passage 218 is threaded at 219 to receive a suitable pipefitting for the outlet line from the pump.

The end plate 143 is provided with an axial extension 222 which extendsinto outlet passage 213 to seal off the latter at the inner end. Leakageof the high pressure outlet fluid past extension 222 is prevented by anO-ring seal 223 on its outer periphery. A reduced axial bore 224 extendsthrough the extension 222 between outlet passage 218 and the axial boreor chamber 148 within the guide portion 147. A valve spool 226 isslidably fitted withinthe axial bore 224 and has outer and inner reducedannular portions 227 and 228 which define a land portion 229 betweenthem. A passage 231 connects the outlet passage 218 to the outer reducedannular portion 227, and another passage 232 extends between the innerreduced portion 228 and the chamber 141 within the pump housing. Anannular port 233 is formed on extension 222 opposite the land 229 and isconnected through passage 243 to chamber 148.

The inner end of valve spool 226 extends into the axial bore 148 andsupports a cap 236. The cap 236 is pro vided with a socket on its innerface to receive a ball 237 which is also received in a spring abutmentmember 238. A control spring in the form of helical compression spring239 extends longitudinally within the axial bore 148 and seats at itsone end against the spring abutment 238 and at its other end againstanother abutment 241 which is secured in the outer end of axial bore 148by means of a snap ring 242. Adjacent the spring abutment member 2.41, aradial passage 24:; extends outward through the wall of tubular guideportion 147 to connect the axial bore 143 with annular passage 246formed in the cylinder block 175 about the guide portion 147. In turn,annular passage 246 connects with an axial cylinder bore 247 formedwithin the cylinder block 175 about tubular guide portion 147. A piston24 8 is secured on the end of tubular guide portion 147 by a snap ring249 and makes sealing contact with the walls of the axial cylinder bore24-7 to form an expansible fluid chamber 256- between the cylinder blockand the piston.

In order to provide an external control for shifting the cylinder block175, a control shaft housing 252 projects downwardly below the pumphousing 14%, and a transverse control shaft 255 is journaled withinhousinng 252. A lever 254 is secured to control shaft 253 within thehousing 252 and extends upward toward the cylinder block 175 where ithas a ball end 256 adapted to fit within the filling slot 183 on thecylinder block. A longitudinal slot 257 is formed on the outer surfaceof cylinder block 175 to allow lever 254 and ball end 256 to move freelyforward toward the spring abutment plate 1' 8 so that the lever 254 canbe rotated out of contact with the sides of the filling slot 183 whenthe pump is under automatic control.

The control shaft 253 extends outward to the exterior of the pump, andas shown more clearly in FIG. 9, an arm 259 is secured on the outer endof the shaft adjacent an indicia plate 261. A handle 262 is pivotallymounted on the upper end of arm 259 by pivot pin 263, and a torsionspring 264 it fitted over the projecting end of pivot pin 263 and isconnected both to a pin 266 on arm 259 and to another pin 267 on handle262. Torsion spring 264 provides a spring-loaded connection between thehandle and arm and is positioned to normally bias the handle 262 intocontact with a stop pin 268 on arm 259. Thus, the handle and arm arenormally in alignment as indicated in FIG. 9 but force applied to thearm 259 by rotation of the control shaft 253 as the cylinder block ismoved toward the outlet housing under operation of the automatic controlwill cause the handle 262 in the operators hand to pivot around pivotpin 263 against the force of torsion spring 264 to prevent possibleinjury to the operators hand if he is holding the handle 262 forshifting the cylinder block under manual control when the automaticcontrol comes into operation.

The operation of this embodiment of the pump can be seen more clearly inconjunction with FIGS. 7 and 8. When the cylinder block 175 is in theintermediate position as shown in FIG. 6, the filling slot 183 willpresent a maximum port area at the rearward reversal of the piston sothat the cylinder bore will be completely filled at each reversal andall the fluid within the cylinder 'bore corresponding to thedisplacement of the piston stroke will 'be pumped out through thereaction piston 269 and port member 2% to the outlet passage 218. If thecylinder block 175 is shifted by means of the manual control levertoward the stop plate 150, the forward edge 134 of filling 183 will beshifted toward the piston head 166 to reduce the efiective port area ofthe filling slot. As has been previously described, the reduction inport area for the cylinder serves to throttle the flow of fluid into thecylinder bores and therefore reduces the effective output volume of thepump toward the zero output condition which occurs when the cylinderblock is in the position of FIG. 7, so that the filling slot 183 isnever uncovered by the piston head. It should be noted that since thespring abutment plate 178 is limited in its range of movement by thesnap ring 181, there are no pumping or spring biasing forces exerted onthe cylinder block 175 when the latter is between the position shown inFIG. 6 and that shown in FIG. 7. Therefore, it requires no noticeableeffort on the part of the operator to shift the cylinder block withinthis range by means of the manual control handle.

The automatic control operates to shift the cylinder block to reduce theeffective output volume of the pump whenever the pressure within theoutlet passage 218 exceeds a predetermined level. When the pressure inthe outlet passage 218 is well below this predetermined level, thecontrol spring 239 acting through abutment 238, ball 237 and cap 23-6will bias the valve spool 226 in a leftward direction as shown in FIG.6. With the valve spool 226 in this position, the land 229 is shifted tothe left of the annular port 233 which is then connected by the innerreduced annular portion 228 to the drain passage 232 leading to theinterior of the pump housing. Since the annular port 233 is connectedthrough passage 243 to the axial bore 148, and the latter is in turnconnected through the radial passage 244 to the chamber 259, this latterchamber will therefore be at the low pressure corresponding to that ofthe fluid within the pump housing chamber 141. Thus the biasing force ofthe compression springs 203 on the reaction pistons 29% will bias thespring abutment plate 178 toward the right and maintain the cylinderblock 175 shifted in the position of FIG. 6 to insure that the pump isoperating at maximum output volume, unless the operator through themanual control lever should shift the cylinder rblock further toward thestop plate 156 to reduce the volume by manual control.

When the pressure within the outlet passage 21% builds up to the controlpressure level, this pressure exerts a force on the end of the valvespool 2 26 tending to shift it toward the right as shown in FIG. 6against the biasing force of the control spring 239. When this biasingforce of the fluid pressure is sufficiently great to shift the valvespool to a position where the land 229 is to the right of the annularport 223, this latter port will be connected through the outer reducedannular portion 227 on the valve spool to the passages 231 leading tothe outlet passages 21% Fluid under high pressure then enters throughthe passages 231, past the outer reduced annular portion 227 to theannular port 233, whence it flows through passage 243 into the axialbore 148. From axial bore 148, the high pressure fluid enters thechamber 250 to expand the size of that chamber by shifting the cylinderblock 175 toward the outlet housing 144.

As the cylinder block 175- is shifted, it moves the spring abutmentplate 178 away from the snap ring stop 181 to compress the springs 263on the reaction pistons. The shifting of the cylinder block in thisdirection serves to shift the forward edge 184 of the filling slot 183closer to the end of the reaction piston and tothe end of thecompression stroke of the pistons 185. Thus the movement of the cylinderblock in this direction through the operation of the automatic controlreduces the effective output volume of the pump by the spill typecontrol in a manner similar to the manual control in the embodiment ofFIGS. 1 through 5.

When the reduction in the effective output volume of the pump serves todrop the pressure within outlet passage 218 to the preselected value,the valve spool 226 will be shifted to the intermediate position of FIG.6, where the land 22 9 blocks off the annular port 233 to preventfurther flow of fluid either into or out of the chamber 251). It will beseen that the forces on the valve spool 226' tending to admit fluid intothe chamber 25% depend solely upon the pressure in the outlet passage218, While the forces tending to shift the valve spool 226 toward theleft to connect the chamber 250 with the pump housing chamber 141 arethe sum of the biasing force of the control spring 239, and the pressurewithin the chamber 254) and axial bore 148 acting on the inner end ofthe valve spool 226, and these pressures will be dependent upon theamount of compression of the compression springs 293 biasing thecylinder block toward the maximum volume position.

If, when the cylinder block 175 is shifted toward the minimum outputvolume position as shown in FIG. 8,

with the cylinder block in the position where the piston head 186 failsto cover the filling slot 183 to seal off the intake port and hence nofluid is pumped into the outlet passage 218, an increase in demand atthe outlet passage 218 will cause the pressure therein to decrease. Thecontrol mechanism will therefore act to shift the cylinder block backtoward the maximum position to increase the output volume of the pump tomaintain the selected pressure in the following manner. Decrease in thepressure at the outlet, passage 218 will cause the valve spool 226 to beshifted toward the left as a result of the aforesaid forces of thecontrol spring 239 and the fluid pressure Within chamber 259. The land229 will then be shifted to the left of the annular port 223, and theaxial bore 148 and chamber 250 will then be connected to the pumphousing chamber 141 in the aforedescribed manner. The biasing force ofthe compression spring 203 will then tend to shift the spring abutmentplate 178 and cylinder block 175 toward the right and force the fluidwithin chamber 250 out into axial bore 148 and hence past the valvespool 226 into the pump housing chamber 141. This action will continueuntil either the cylinder block 175 has been shifted back to the maximumvolume position where the spring abutment plate 178 is in contact withthe snap ring stop 181, or else the pressure within the outlet passage218 rises to a point where the valve spool 226 is shifted back towardthe right so that land 229 blocks off the annular port 233.

If the pump is in operation under manual control with the operatinghandle 262 moved to shift the cylinder block 175 to a position where itis intermediate the spring abutment plate 178 and the stop plate 150,and the pressure within the outlet passage 218 should exceed theautomatic control level, the valve spool 226 will be shifted in to admitfluid into chamber 250 and thereby force the cylinder block 175 past themaximum volume position toward a reduced volume position within thespill control range. Thus the automatic control serves as a pressureoverload protective device to prevent the operator from exceeding themaximum pressure for the system when he is operating the pump undermanual control. When it is intended to operate the pump using automaticcontrol, the control handle 262 will be shifted to the lefthand positionas seen inFIG. 9, so that the ball end 256 on lever 254 is shiftedtoward the end of the longitudinal slot 257 adja cent the springabutment plate 178. This insures that position of the cylinder block 175under the automatic control will not impart any motion to the lever 254and hence to the operating handle 262. However, if the handle should beleft in the righthand position as shown in FIG. 9, and if the automaticcontrol should take over to shift the cylinder block 175 toward theleft, the motion of the cylinder block 175 will force the lever 254 tothe left, since the forces of the pressure within the chamber 250biasing the cylinder block in that direction are relatively highcompared to the forces which can be applied to the cylinder block byhand. If the operator is holding the handle 262 under these conditions,the rotation of the control shaft 253 and hence arm 259 will cause thetoggle joints between the arm and handle to break against the biasingforce of torsion spring 254 and the control shaft 253 will be able torotate without movement of the handle 262 and the latter will not beforced from the operators hand in a manner which could cause seriousinjury.

While several embodiments of the invention have been shown in thedrawings and described hereinabove in considerable detail, it isunderstood that this invention can take many other forms andembodiments, and that such forms and embodiments as may occur to thoseskilled in the art may be resorted to without departing from the scopeof the invention as defined in the following claims.

What is claimed is:

1. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber,

an outlet port on said pump housing, a cylinder block mounted forslidable movement within said fluid chamber along a longitudinal axis, aplurality of cylinder bores in said cylinder block, a piston within eachof said cylinder bores, means in said pump housing to progressivelyreciprocate said pistons in said cylinder bores between forward andretracted positions, means connecting each of said cylinder bores tosaid outlet port, an inlet port for each cylinder bore in said cylinderblock, said port having axially spaced edges, said cylinder blockdefining a maximum volume position when the piston head is intermediatesaid port edges when the piston is in the retracted position, means toshift said cylinder block in one direction from said maximum volumeposition to reduce the effective area of said cylinder bore inlet ports,and means to shift said cylinder block in the other direction from saidmaximum volume position to reduce the effective length of the pumpingstroke of the pistons.

2. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber, an outlet port on said pumphousing, a cylinder block mounted for slidable movement within saidfluid chamber along a longitudinal axis, a plurality of cylinder boresin said cylinder block, a piston within each of said cylinder bores,means in said pump housing to progressively reciprocate said pistons insaid cylinder bores between forward and retracted positions, meansconnecting each of said cylinder bores to said outlet port, an inletport for each cylinder bore in :said cylinder block, said port havingaxially spaced edges, said cylinder block defining a maximum volumeposition when the piston head is intermediate said port edges when thepiston is in the retracted position, manual control means on theexterior of said pump housing adapted to shift said cylinder block alongsaid longitudinal axis, said manual control means being operable toshift said cylinder block in one direction from said maximum volumeposition to reduce the effective area of said cylinder bore inlet ports,said manual control means being operable to shift said cylinder block inthe other direction from said maximum volume position to reduce theeffective length of the pumping stroke of the pistons.

3. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber, an outlet port on said pumphousing, a cylinder block mounted for slidable movement within saidfluid chamber along a longitudinal axis, a plurality of cylinder boresin said cylinder block, a piston Within each of said cylinder bores,means in said pump housing to progressively reciprocate said pistons insaid cylinder bores between forward and retracted positions, check valvemeans connecting each of said cylinder bores to said outlet port, aninlet port for each cylinder bore in said cylinder block, said porthaving axially spaced edges, said cylinder block defining a maximumvolume position when the piston head is intermediate said port edgeswhen the piston is in the retracted position, manual control means toshift said cylinder block in one direction from said maximum volumeposition to reduce the effective area of said cylinder bore inlet ports,and control means responsive to fluid pressure in said outlet port toshift said cylinder block in the other direction from said maximumvolume position to reduce the effective length of the pumping stroke ofthe pistons.

4. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber, an outlet port on said pumphousing, a cylinder block mounted for slidable movement Within saidfluid chamber along a longitudinal axis, a plurality of cylinder boresextending axially through said cylinder block, a piston within one endof each of said cylinder bores, wobble plate means in said pump housingto progressively reciprocate said pistons in said cylinder bores betweenforward and retracted positions, a tubular reaction piston within theother end of each of said cylinder bores, said reaction pistons havingthe same diameter as said pistons, check valve means on said pumphousing adjacent each of said tubular reaction pistons, means connectingeach of said check valve means to said outlet port, an inlet port foreach cylinder bore in said cylinder block, said port having axiallyspaced edges, said cylinder block defining a maximum volume positionwhen the piston head is intermediate said port edges when the piston isin the retracted position, means to shift said cylinder block in onedirection from said maximum volume position to reduce the effective areaof said cylinder bore inlet ports, and means to shift said cylinderblock in the other direction from said maximum volume position to reducethe effective length of the pumping stroke of the pistons.

5. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber, an outlet port on said pumphousing, a cylinder block mounted for slidable movement within saidfluid chamber along a longitudinal axis, a plurality of cylinder boresextending axially through said cylinder block, a piston within one endof each of said cylinder bores, wobble plate means in said pump housingto progressively reciprocate said pistons in said cylinder bores betweenforward and retracted positions, a tubular reaction piston within theother end of each of said cylinder bores, said reaction pistons havingthe same diameter as said pistons, check valve means on said pumphousing adjacent each of said tubular reaction pistons, passage meansconnecting each of said check valve means to said outlet port, an inletport for each cylinder bore in said cylinder block, said port havingaxially spaced edges, said cylinder block defining a maximum volumeposition when the piston head is intermediate said port edges when thepiston is in the retracted position, manual control means on theexterior of said pump housing operable to shift said cylinder blockalong said longitudinal axis, said manual control means being operableto shift said cylinder block in one direction from said maximum volumeposition to reduce the effective area of said cylinder bore inlet ports,said manual control means being operable to shift said cylinder block inthe other direction from said maximum volume position to reduce theeffective length of the pumping stroke of the pistons.

6. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber, an outlet port on said pumphousing, a cylinder block mounted for slidable movement within saidfluid chamber along a longitudinal axis, a plurality of cylinder boresextending axially through said cylinder block, a piston within one endof each of said cylinder bores, wobble plate means in said pump housingto progressively reciprocate said pistons in said cylinder bores betweenthe forward and retracted positions, a tubular reaction piston withinthe other end of each of said cylinder bores, said reaction pistonshaving a diameter equal to the diameter of said pistons, check valvemeans on said pump housing adjacent each of said tubular reactionpistons, passage means connecting said check valve means to said outletport, an inlet port for each cylinder bore in said cylinder blockadjacent the head of the piston therein when the piston is in theretracted position, manual control means on said pump housing operableto shift said cylinder block in one direction to reduce the effectivearea of said cylinder bore inlet ports, and control means responsive tofluid pressure in said outlet port to shift said cylinder block in theother direction to reduce the effective length of the pumping stroke ofthe pistons.

7. A pump comprising a pump housing providing a generally cylindricalfluid chamber therein, and inlet port to said fluid chamber, an outletport on said pump housing, a guide member secured to said pump housingand extending longitudinally coaxial with said fluid chamber, a cylinderblock mounted for axially slidable movement on said guide member, aplurality of cylinder bores extending axially through said cylinderblock, a piston within one end of each of said cylinder bores, wobbleplate drive means in said pump housing to progressively reciprocate saidpistons in said cylinder bores between for- Ward and retractedpositions, a tubular reaction piston within the other ends of each ofsaid cylinder bores, said reaction pistons having the same diameter assaid pistons and being axially slidable relative to said cylinder blockand said pump housing, check valve means on said pump housing adjacenteach of said tubular reaction pistons, spring means maintaining saidreaction piston in sealing engagement with said check valve means, meansconnecting each of said check valve means to said outlet port, an inletport for each cylinder bore in said cylinder block adjacent the head ofthe piston therein when the piston is in the retracted position, manualmeans to shift said cylinder block in one direction to reduce theeffective area of said cylinder bore inlet ports, and control meansresponsive to fluid pressure in said outlet port to shift said cylinderblock in the other direction to reduce the effective length of thepumping stroke of the piston.

8. A pump comprising a pump housing providing a generally cylindricalfluid chamber therein, an inlet port to said fluid chamber, an outletport on said pump housing, a cylinder block slidably journaled in saidpump housing for longitudinal movement therein, guide means preventingrotation of said cylinder block in said pump housing, a plurality ofcylinder bores extending axially through said cylinder block, a pistonwithin one end of each of said cylinder bores, wobble plate drive meansin said pump housing to progressively reciprocate said pistons in saidcylinder bores between forward and retracted positions, a tubularreaction piston within the other end of each of said cylinder bores,said reaction pistons having the same diameter as said pistons and beingaxially slidable relative to said cylinder block and said pump housing,check valve means on said pump housing adjacenteach of said tubularreaction pistons, spring means maintaining said reaction pistons insealing engagement with said check valve means, passage means connectingeach of said check valve means to said outlet port, an inlet port foreach cylinder bore in said cylinder block, said port having axiallyspaced edges, said cylinder block defining a maximum volume positionwhen the piston head is intermediate said port edges when the piston isin the retracted position, manual control means on the exterior of saidpump housing operable to shift said cylinder block longitudinally withinsaid pump housing, said manual control means being operable to shiftsaid cylinder block in one direction from said maximum volume positionto reduce the effective area of said cylinder bore inlet ports, saidmanual control means being operable to shift said cylinder block in theother direction from said maximum volume position to reduce theeffective length of the pumpin stroke of the pistons.

9. A pump comprising a pump housing providing a fluid chamber therein,an inlet port to said fluid chamber, an outlet port on said pumphousing, a cylinder block mounted for slidable movement within saidfluid chamber along a longitudinal axis, a plurality of cylinder boresextending axially through said cylinder block, a piston Within one endof each of said cylinder bores, wobble plate drive means in said pumphousing to progressively reciprocate said pistons in said cylinderbores, a tubular reaction piston within the other end of each of saidcylinder bores, said reaction piston having the same diameter as saidpiston and being axially slidable relative to said cylinder block andsaid pump housing, check valve means on said pump housing adjacent eachof said tubular reaction pistons, spring means maintaining said reactionpistons in sealing engagement with said check valve means, passage meansinterconnecting said check valve means and said outlet port, an inletport for each cylinder bore in said cylinder block, said port havingaxially spaced edges, said cylinder block defining a maximum volumeposition when the piston head is intermediate said port edges when thepiston is in the retracted position, a rocker 15 shaft in said pumphousing extending transversely to said longitudinal axis, meansinterconnecting said rocker shaft and said cylinder block wherebyrotation of said rocker shaft moves said cylinder block axially, levermeans exteriorly of said pump housing for rotating said rocker shaft,whereby movement of said control lever in one direction from the maximumposition with respect to said pump housing shifts the position of saidcylinder block to reduce the effective output volume of the pump bydecreasing the effective length of the stroke of said pistons, andmovement of said lever in the other direction from said maximum positionshifts said cylinder block to reduce the effective output volume of thepump by reducing the efiective inlet port area.

References Cited in the file of this patent UNITED STATES PATENTSLOrange May 19, 1936 Cameron Feb. 13, 1945 Tuck et al July 4, 1961FOREIGN PATENTS Great Britain Dec. 7, 1933

1. A PUMP COMPRISING A PUMP HOUSING PROVIDING A FLUID CHAMBER THEREIN,AN INLET PORT TO SAID FLUID CHAMBER, AN OUTLET PORT ON SAID PUMPHOUSING, A CYLINDER BLOCK MOUNTED FOR SLIDABLE MOVEMENT WITHIN SAIDFLUID CHAMBER ALONG A LONGITUDINAL AXIS, A PLURALITY OF CYLINDER BORESIN SAID CYLINDER BLOCK, A PISTON WITHIN EACH OF SAID CYLINDER BORES,MEANS IN SAID PUMP HOUSING TO PROGRESSIVELY RECIPROCATE SAID PISTONS INSAID CYLINDER BORES BETWEEN FORWARD AND RETRACTED POSITIONS, MEANSCONNECTING EACH OF SAID CYLINDER BORES TO SAID OUTLET PORT, AN INLETPORT FOR EACH CYLINDER BORE IN SAID CYLINDER BLOCK, SAID PORT HAVINGAXIALLY SPACED EDGES, SAID CYLINDER BLOCK DEFINING A MAXIMUM VOLUMEPOSITION WHEN THE PISTON HEAD IS INTERMEDIATE SAID PORT EDGES WHEN THEPISTON IS IN THE RETRACTED POSITION, MEANS TO SHIFT SAID CYLINDER BLOCKIN ONE DIRECTION FROM SAID MAXIMUM VOLUME POSITION TO REDUCE THEEFFECTIVE AREA OF SAID CYLINDER BORE INLET PORTS, AND MEANS TO SHIFTSAID CYLINDER BLOCK IN THE OLTHER DIRECTION FROM SAID MAXIMUM VOLUMEPOSITION TO REDUCE THE EFFECTIVE LENGTH OF THE PUMPING STROKE OF THEPISTONS.